FERGUSON, Mo. — With a controversial curfew lifted and the National Guard mobilized, protests started peacefully Monday but as the evening wore on clashes with police escalated until the now sadly familiar scene of tear gas being fired at protesters began.

A standoff between police and demonstrators in this city that has been wracked by grief and rage over the fatal police shooting of an unarmed black teenager began after members of the crowd became confrontational and bottles were thrown at police officers.

Police began to lob tear gas canisters and stun grenades toward protesters who had ignored warnings to clear the street and disperse.

Police said a Molotov cocktail was hurled at officers and a civilian in a car near the scene of the confrontation was shot, CNN reported.

Bishop Edwin Bass of the Church of God in Christ, who was on the scene urging people to remain calm, said, "The crowd shifts substantially about 8 p.m. A lot of the family people, and people here for legitimate protest reasons, leave. The people who are here for mayhem, confusion and chaos come out."

That pattern appeared be playing out Monday night, as Capt. Ron Johnson, regional head of the Missouri State Highway patrol, said numerous arrests had been made.

Hundreds of protesters approached a line of police and many shouted while face-to-face with the officers. Amid the tense situation, a group of people trying to keep the peace locked arms and managed to position themselves between the more confrontational protesters and the police line.

The crowd was ordered to disperse by officers in armored trucks that appeared on the scene, but the protesters continued to march down the street.

Missouri Gov. Jay Nixon on Monday dropped the curfew that had been in effect for two nights in an ill-fated effort to curb the violence and chaos that have ripped this city since Michael Brown, 18, an unarmed black pedestrian, was shot to death by white police officer Darren Wilson, 28, on Aug. 9,

Nixon announced that the National Guard would assume "limited responsibilities" to help keep order during nighttime protests over the shooting.

"With these additional resources in place, the Missouri State Highway Patrol and local law enforcement will continue to respond appropriately to incidents of lawlessness and violence, and protect the civil rights of all peaceful citizens to make their voices heard," Nixon said in a written statement. "We will not use a curfew tonight."

A grand jury may begin hearing the case on Wednesday, according to the Associated Press. It was unclear how long it might take for a decision on whether Wilson should face criminal charges for Brown's death.

Meanwhile, President Obama announced that Attorney General Eric Holder will go to Ferguson on Wednesday to meet with local leaders as well as FBI and Justice officials who are conducting an independent federal civil rights investigation into the shooting.

At a late afternoon news conference, Obama once again called for understanding and calm on Ferguson's streets.

"While I understand the passion and anger that arise over the death of Michael Brown, giving in to that anger by looting ... only serves to raise tensions and stir chaos,'' he said, adding, "There's no excuse for excessive force by police or any action that denies people the right to protest peacefully."

But there continued to be clashes between law enforcement officials and those gathered on Ferguson's streets.

People march down the street after a standoff with police Monday, during a protest for Michael Brown, who was killed by a police officer Aug. 9 in Ferguson, Mo.(Photo: Charlie Riedel, AP)

Scott Olson, a news photographer with Getty Images, became the latest journalist to be arrested, according to Pancho Bernasconi, Getty's vice president for news. Olson's arrest was captured by one of his Getty colleagues, Joe Raedle. He was later released, and in a statement, Getty said he would continue working in Ferguson.

Others had their own tense encounters with the police. In one instance during the afternoon, St. Louis County police officers arrested a man walking on the sidewalk.

Capt. Johnson said one man who was arrested for failure to disperse had threatened to hurt police officers.

"That's not not freedom of speech when you say I'm going to hurt you," Johnson said. "That's not freedom of speech."

Two police officers tackled the man and took him to the ground while onlookers shouted that the man wasn't doing anything wrong.

"I didn't see anybody behaving in any way that would instigate for the police to do anything," said Ben Mengis, 55, of St. Louis County, who said he was standing 10 feet from the incident. "He did not do anything."

A police spokesman could not be reached for comment.

At 5:15 p.m. local time, as CNN's Don Lemon did a live report on the sidewalk on West Florissant Avenue, St. Louis County police pushed him and a group of protesters surrounding him backward on the sidewalk.

A minute or two later, one of the protest leaders led a large group of protesters to a parking lot on the other side of the street.

When small groups of protesters gathered, police ordered them away from some of the spots that have been prone to late-night upheaval. As evening approached, the police presence in the area near West Florissant Avenue and Ferguson Avenue was increasing sharply, with officers from the Missouri State Highway Patrol, St. Louis County police and St Louis Metropolitan police.

Around 5:50 p.m. local time, an official in a police vehicle drove along West Florissant telling people via loudspeaker that they had to keep moving if they were on the sidewalk. If they stood still, he said, they would be given one warning and then would be arrested.

Capt. Johnson said he planned to prevent a repeat of the violence that erupted the previous night. "We have an operational plan to address that and we're going to put it in place," he said. "Our city cannot afford another night (like) last night. We can't."

He said the rule requiring that protesters on the sidewalk keep moving was meant to prevent troublemakers from infiltrating groups of legitimate demonstrators.

"They have to keep walking," Johnson said. "We're not going to let groups congregate and build into larger groups. That's what causes the problem."

He said that people's' Constitutional right to peaceful assembly was not being violated.

With the National Guard in Ferguson, Obama said that in a conversation with the governor, he "expressed an interest in making sure that ... the National Guard is used in a limited and appropriate way.''

"I'll be watching over the next several days to see whether in fact it's helping rather hindering'' progress, the president said.

Outrage over Brown's shooting spurred protests in this predominantly black city of 21,000 on the outskirts of St. Louis. When demonstrators met with a heavy police presence, fierce nightly clashes erupted.

The midnight-to-5 a.m. curfew that was lifted Monday did little to curb the violence and looting. A representative of the Nation of Islam said his group would ask protesters to go home early Monday night. He noted that the group can't force people to leave but cited "the militarized police force" and the National Guard as reasons to do so.

"We are going to tell them that this is a different day now with the National Guard in," said Akbar Muhammad, international representative of the Nation of Islam. "We want them to leave by sunset."

Muhammad also said at a press conference near the Ferguson Police Department that his group is looking for a venue to hold a youth rally, "like a town hall meeting" for local youths.

The latest unrest led officials to close all schools in the Ferguson-Florissant School District on Monday. School had already been postponed last week due to the violence.

Nixon ordered the National Guard into Ferguson hours after police cited "preplanned" acts of aggression by protesters Sunday night and early Monday morning. Protesters shot at police, threw Molotov cocktails at officers, looted businesses and carried out a "coordinated attempt" to block roads and overrun the police's command center, the governor's office said in a written statement.

"We are all frustrated and looking for justice to be achieved regarding the shooting death of Michael Brown," Nixon's statement said. "As the dual investigations continue into what happened nine days ago at Canfield Green, we must defend Ferguson from these violent interlopers so that the peaceful protests can operate in peace and the search for answers and justice can continue."

Earlier Monday, lawyers for Brown's family released details of the private autopsy done at the request of the family by pathologist Michael Baden. The preliminary report indicated Brown was shot six times. Only one of the shots was fatal, Baden said.

"It verifies the worst that the family thinks happened — that he was executed," family attorney Benjamin Crump said. "It confirms what the witnesses said, that this was an execution."

Officer Wilson has supporters. More than 100 people rallied Sunday in downtown St. Louis on his behalf. The rally was organized through social media and the Support Darren Wilson Facebook page, which was created Saturday. By noon Monday, the page had drawn more than 24,000 "likes."

More than two hours before a second midnight curfew was set to begin Sunday night, police fired tear gas at hundreds of angry protesters who were marching down the town's main thoroughfare toward a police command center.

"Based on the conditions, I had no alternative but to elevate the level of our response," said the highway patrol's Johnson. "We had to act to protect lives and property."

At least two people were injured, including one who was shot, Johnson said. Seven or eight people were arrested and will be charged with failure to disperse, police said.

"Police were shot at, makeshift barricades were set up to block police, bottles and rocks were thrown at police," Johnson said.

Some protesters said no one threw Molotov cocktails.

Renita Lamkin, 43, the pastor of St. John African Methodist Episcopal Church in St. Charles, Mo., has been acting as a peacekeeper, urging people to remain calm.

"That is not true," she said when asked about claims that protesters threw Molotov cocktails.

Contributing: Yamiche Alcindor

Gunshots have been heard in Ferguson, Missouri, where demonstrators are protesting the police shooting death of 18-year-old Michael Brown. Police ordered the demonstrators to disperse on Sunday night and fired tear gas. (Aug. 18)
AP

A member of the Federal Protective Service asks demonstrators to stay off the steps leading to the Thomas F. Eagleton federal courthouse during a protest in St. Louis. About 100 protesters marched from city hall to the courthouse as they continue to press for broader reforms to local and federal law enforcement following the shooting death of Michael Brown by police. Jeff Roberson, AP

Members of the Tauheed Youth Group pray with demonstrators and members of the 'Justice for Michael Brown Leadership Coalition' during a march near the Buzz Westfall Justice Center in Clayton, Mo. Larry W. Smith, epa

People pray after marching about a mile to the police station to protest the shooting of teenager Michael Brown in Ferguson, Mo. Brown's shooting on Aug. 9 by a Ferguson police officer has sparked more than week of protests, riots and looting in the St. Louis suburb. Charlie Riedel, AP

U.S. Attorney General Eric Holder shakes hands with Bri Ehsan, 25, following his meeting with students at St. Louis Community College-Florissant Valley in Ferguson, Mo. Holder was in Ferguson to oversea the federal government's investigation into the shooting death of 18-year-old Michael Brown by a police officer on Aug. 9th. Pablo Martinez Monsivais, pool

A citizen peacekeeper tries to keep protesters back as police advance on Aug. 18 in Ferguson, Mo. The Aug. 9 shooting of Michael Brown by a police officer has touched off demonstrations in the St. Louis suburb where police have used riot gear and tear gas against protesters. Christian Gooden, St. Louis Post-Dispatch, via AP

Attorney Benjamin Crump, left, holds a diagram produced during a second autopsy of shooting victim Michael Brown as forensic pathologist Michael Balden speaks at a news conference Aug. 18 in Ferguson, Mo. The independent autopsy shows Brown was shot at least six times on Aug. 9 by a Ferguson police officer. Jeff Roberson, AP

Tear gas canisters hit the pavement around a woman demonstrating on Aug. 17 against the killing of Michael Brown, 18, by a police officer in Ferguson, Mo. Despite the Brown family's continued call for peaceful demonstrations, violent protests have erupted nearly every night since his Aug. 9 death. Scott Olson, Getty Images

Demonstrators speak to Capt. Ronald Johnson of the Missouri State Highway Patrol, who was appointed by the governor to take control of security operations in the city of Ferguson. Joe Raedle, Getty Images

Lesley McSpadden and Michael Brown, the parents of slain 18-year-old Michael Brown, attend an event for their son at the Greater Grace Church in Ferguson, Mo. The event was lead by the Rev. Al Sharpton in support of justice for Michael Brown. Joe Raedle, Getty Images

Police fire tear gas early Aug. 17 at a crowd of protesters who disobeyed the midnight curfew in Ferguson, Mo. People are protesting the shooting death of Michael Brown, 18, on Aug. 9. Roberto Rodriguez, european pressphoto agency